272 Auxins in Agriculture 



bud is perhaps responsible for the fact that foHar sprays are much 

 more effective than dust treatments of the tubers and roots themselves. 

 Auxins applied to the foliage before the plant dies down are trans- 

 located into the storage organs where they can effectively inhibit 

 sprouting in storage. It appears that in general early foliage applica- 

 tions are more effective in controlling sprouting than are late applica- 

 tions, but unfortunately early applications are also more damaging 

 to the plants. The success of such applications in each crop is de- 

 pendent upon the finding of a time of application which will minimize 

 damage and still give effective sprouting control. 



STORAGE QUALITY 



Applications of auxins to prevent sprouting of tubers and bulbs 

 can have rather important effects on the quality of the stored prod- 

 uct. It has been reported that pre-harvest foliar sprays of auxins on 

 potatoes decrease the specific gravity of the tubers and increase the 

 occurrence of potato scab (Smith et al, 1947). The high incidence of 

 scab is apparently associated ivith the normal scabies pathogen, and 

 somehow the tuber is simply more susceptible to its attack (Wood 

 and Ennis, 1951). Such sprays also lower the amount of reducing sugars 

 in the potato, which is a desirable characteristic. It has been found 

 that tubers from auxin-treated plants are perfectly effective for seed 

 stock the following year (Ellison and Smith, 1948). 



The control of sprouting in carrots with auxin treatment of the 

 roots in storage is generally damaging, although the use of methyl 

 ester of naphthaleneacetic acid appeared promising (Dallyn and 

 Smith, 1952). The auxins are very prone to cause callus formation 

 and sprouting of secondary roots from the carrot. Foliar sprays of 

 auxins can sometimes overcome this quality limitation (Wittwer et al, 

 1950). 



The effects of maleic hydrazide on storage quality are not as well 

 defined as are the effects of auxins. Potatoes from plants receiving 

 foliar sprays of maleic hydrazide have been found to contain a low 

 sugar content (Paterson et al, 1952). Onions treated similarly have 

 shown no change in either carbohydrate content or in soluble nitro- 

 gen fractions (Wittwer and Sharma, 1950). The storage quality of 

 beets has been reported to be improved by maleic hydrazide treat- 

 ment, not through effects on sprouting but rather by prevention of 

 sugar loss during storage (Wittwer and Hansen, 1951). 



The effect of maleic hydrazide in improving storage quality of 

 apples which have been treated Avith auxin to control abscission is 

 discussed in chapter XIII. 



